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110.7%,906. PATENTED JAN. 5, 1904.

' B. B. Y-A'XLEY.

TRANSMITTER.

APPLICATION nmm APR.13, 1901.

no MODEL. 7

. tion for assembling.

UNITED STATES Patented January 5, 1904.

PATENT OFFICE.

ERNEST E. YAXLEY, OF CHICAGO, ILLINOIS, ASSIGNOR TO AMERICAN ELECTRIC TELEPHONE COMPANY, OF CHICAGO, ILLINOIS, A CORPO- RATION.

TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 748,906, dated January 5, 1904.

Application filed April 13, 1901.

To aZZ whom it may concern:

Be it known that I, ERNEST E. YAXLEY, a citizen of the United States of America, and a resident ofOhicago, Cook county, Illinois, have in vented a certain new and useful Transmitter, of which the following is a specification.

My invention relates to improvements intelephone-transmitters, and has special reference to those of the granular-carbon type.

It has for its objects the production of an improved transmitter in which a Wide variation of pressure among the carbon granules is obtainable and in which the carbon granules are maintained in a sensitive and separated condition. Y

Further objects are the provision of certain details and features of improvement whereby an efficient, durable,convenient,and comparatively cheap instrument is secured.

To the accomplishment of these and such other objects as may hereinafter appear the invention comprises a transmitter of substantially the usual form in which granules of the carbon are firmly attached to the inner surface of an electrode, preferably the diaphragm. The back electrode is provided with concentric rings, into which the carbon grains wedge to make good contact therewith. The adj listing-screw in the back hub is locked in place and in addition is so formed that it is impossible to grasp it with pliers with suflicient force to break the locking means or move it.

The invention further comprises the novel details of construction hereinafter described, and particularly pointed out in the appended claims,reference being had to the accompanying drawings, forminga part hereof, in which the same reference characters designate like parts throughout the several views, and in which- Figure 1 is a sectional view on the line 1 l of Fig. 2. Fig. 2 is a sectional view on the line 2 2 of Fig. 1. Fig. 3 is a view showing the several parts of the transmitter in posi- Fig. 4 is a perspective view of the diaphragm, showing its inner surface. Fig. 5 is a plan view of the back electrode.

- over to secure the two together.

As is apparent from the figures, the trans- Serial No. 55,760. (No model.)

between them and the front casing being secured to the rear or back casing by the screws 6, threading into flange 9 thereon. A hub or sleeve 7 is fixed centrally to the back face of the case 5, by which it is secured to the transmitter-arm and forms one terminal of the c'ircuit through the transmitter-head.

The diaphragm 8 fits snugly within the annular flange 9, a ring or washer of paper 10, or other suitable material, being placed at the edge of the diaphragm between it and the adjacent portion of the front case 3. Springs 11', carried by posts 12, secured to the under face of the back case 5, bear with their curved double ends 12 upon the edge of the diaphragm 8, as seen in Fig. 1, to hold it snugly against the ring or washer and to com plete the electric circuit therethrough.

A cup-shaped back electrode 15, of brass or other desirable material, having, preferably, concentric grooves 15 is supported in the rear of the diaphragm 8in a supportingdisk 16, suitably spun or hollowed out to seat said electrode 15 therein and is firmly secured to the adj usting-screw 16*, which is adjustably held in the insulating-sleeve 17, secured in the hub 7 by pin 27. The forward end 18 of this screw is reduced or shouldered and passes through a small hole 18 in the stationary electrode 15 and is spun or riveted The edge of said plate or disk 16, which extends outwardly, forms an annular flange about the electrode 15, on which'is carried a ring or strip 20, of felt, plush, or other suitable material, and which bears lightly against the inner face of the diaphragm 8. The edge of the electrode 15 is grooved or shouldered to provide a seat for the edge of a perforated plate or disk 21,in which the perforations are large enough for the carbon granules to pass therethrough. The space between the inner face of the diaphragm and the front or grooved face of the stationary electrode and within the ring 20 is preferably filled with granular carbon, which is thus on both sides of the perforated plate 21.

To the inner surface of the diaphragm 8 mitter has substantially the usual form and IOO and within the limits of the ring 20 a layer 28 of the carbon granules are firmly secured, preferably, by a cement of high conductivity, so as not to increase the resistance to the passage of the electric current. By this arrangement the variable-resistance surfaces or variable-pressure surfaces or contacts are confined to the carbon itself, as there is no change of intimacy of contact between the carbon and the metallic diaphragm or the electrode so coated, but only among the granules themselves, and in the case of the rear or the stationary electrode the action is similar, for the granules wedge into the rectangular concentric grooves and are held thereby. The perforated diaphragm 21 serves to not only increase the action surface of the stationary electrode, but to keep the carbon loose and in a sensitive state.

Of course it will be understood that the form of the electrodes need not be circular or the grooves concentric and exactly rectangular or square in cross-section, so far as some features of my invention are concerned, and the grooves may also be replaced by a layer of granules, as on the diaphragm, though the construction and arrangement shown is preferred. A full layer of the granules upon the diaphragm is more efficient than anything less.

Trouble is often experienced in unauthorized persons changing the adjustment of the hacker stationary electrode after it leaves the factory. To prevent this in my construction, the adjusting-screw 16 is first properly adjusted to the desired position at the factory, and an aperture 25 is drilled through the hub 7, sleeve 17, and into the screw 16, into which an insulating-pin 26 is driven with its outer end either even with or slightly below the surface of the hub 7. It is thus impossible to change the position of the screw without first drilling out the pin or applying snificient force to the screw 16 to break the pin off. To prevent the latter from being easily accomplished, the end of the screw 16 is tapered, as at 38, so that it cannot be easily grasped by ordinary pliers or other instruments outside of a shop. The pin 27 prevents the sleeve 17 from twisting in the hub 7 before the pin 27 is inserted.

The circuit of the instrument, it will be observed, is through the hub 7, back case 5, diaphragm 8, through the granular carbon, to the back electrode 15 and adj usting-screw 16.

While I have described the invention with particular reference to the details of construction, I would have it understood that it is not to be limited thereto, as I hold it to include all such changes, alterations, and modifications as fairly fall Within the scbpe and principle thereof; but

What I do claim, and desire to secure by Letters Patent of the United States, is-

1. In a transmitter the combination of a plate, a diaphragm, a felt ring between the said plate and diaphragm, a cup-shaped back electrode secured to said plate, a perforated disk secured at its edge upon the perimeter of said electrode, and a suitable quantity of granular carbon inclosed between the diaphragm and electrode at each side of said disk.

2. A transmitter comprising a front electrode, a cup-shaped hack electrode, a perforated metal disk secured at its edge to the annular edge of said back electrode, and grannlar carbon inclosed between the two electrodes at each side of said disk.

3. A transmitter comprising a front electrode, a cup-shaped back electrode having its face formed with concentric grooves, a thin perforated sheet-metal disk secured at its;

edge to the circular edge of said back electrode, and granular carbon inclosed between the two electrodes at each side of the said disk.

4. In a transmitter, the combination with a diaphragm, having carbon granules secured to the inner surface thereof and forming one electrode of the transmitter, of another electrode, and granular carbon between said electrodes.

5. In a transmitter, the combination with a diaphragm forming one electrode of the transmitter, or another electrode, and granular carbon between said electrodes, some of said carbon being secured to the surface of the diaphragm.

6. In a transmitter, the combination with a diaphragm forming an electrode of the instrument and having a layer of granular carbon secured to its inner surface, of another electrode, and granular carbon between said electrodes.

7. In a transmitter, the combination with a diaphragm forming one electrode of the transmitter, of a layer of granular carbon cemented to the inner surface of said diaphragm, another electrode of the transmitter, and granular carbon between said electrodes and in contact with the layer.

8. In a transmitter, the combination with a diaphragm having granules of carbon fixed to its inner surface, of another electrode having substantially rectangular grooves therein, and granular carbon therebetween.

9. In a transmitter, the combination with a diaphragm forming the movable electrode of the instrument and having a layer of carbon firmly secured to its inner surface, of a stationary electrode having concentric substantially rectangular grooves therein and granular carbon between said electrodes.

10. In a transmitter, the combination with a diaphragm forming the movable electrode of the instrument and having a layer of carbon firmly secured to its inner surface by cement of high conductivity, of a stationary electrode having substantially rectangular grooves therein and granular carbon between said electrodes.

11. In a transmitter, the combination with a diaphragm having a layer of carbon granules secured to its inner surface, of another electrode, a perforated plate between said electrodes, and granular carbon between said electrodes and on both sides of said plate.

12. In a transmitter, the combination with a diaphragm having a layer of carbon granules secured to its inner face by cement of high conductivity, a stationary electrode having concentric grooves therein substantially rectangular in cross-section, a perforated disk between said diaphragm and electrode,and granular carbon on both sides of said disk and between the layer on the diaphragm and the grooved surface of the stationary electrode.

13. In a transmitter, the combination with a diaphragm, of a stationary electrode having concentric grooves therein substantially rectangular in cross-section, a perforated disk secured at its edge to the perimeter of said electrode, but separated from the grooved surface, a flange at the sides of said electrode, a strip of felt orsimilar substance between said flange and diaphragm, and granular carbon confined by said felt between said diaphragm and electrode and on both sides of the perforated disk.

14. In a transmitter, the combination with the back casing of the transmitter, of a sleeve thereon, an insulating-bushing therein, an electrode, and an adjusting-screw therefor passing through the said insulating-bushing, the said sleeve, bushing and screw having an aperture therethrough, and an insulating-pin driven into saidaperture.

15. In a transmitter, the combination with the back casing of the transmitter, of asleeve thereon, an insulating-bushing therein, an electrode, andan adjusting-screw therefor passing'through the said insulating-bushing, the said sleeve, bushing and screw having an aperture therethrough, and an insulating-pin driven into said aperture, the projecting end of said screw being tapered to prevent readily grasping the same.

16. In a transmitter, the combination with an electrode of theinstrument havingcarbon granules secured to the inner surface thereof, of another electrode, and granular carbon between said electrodes.

17. In a transmitter, the combination with an electrode of the instrument, of another electrode, and granular carbon between said electrodes, some of said carbon being secured to the surface of one of said electrodes.

18. In a transmitter, the combination with two electrodes, of the instrument, a layer of granular carbon secured to one electrode, and a mass of granular carbon therehetween.

19. In atransmitter, the combination of opposing electrodes, one of said electrodes having a layer of granular carbon secured thereto.

20. In a transmitter, the combination with opposing electrodes, of a layer of granular carbon connected to one of said electrodes,

and a mass of granular carbon therebetween.

Signed by me at Chicago, Cook county, Illinois, this 10th day of April, 1901.

ERNEST E. YAXLEY. 

